Spirit is in a valley she probably will be in shadow before the sun gets low enough to shine under her.

Well summarized, Astro0.

I for one am very curious about the "high-centered" feature of the problem: What is she hanging up on? Is it a pile of 'plowed' sand, or a little hummock, or...? Need to understand that to derive a solution since it could make a big difference in driving strategies.

I don't think that we are that far between Tsiolkovsky and HP to prevent some longer shadows.
See Tesh's map for Sol 1871 (where Spirit is right now).
Depends on where the sun is setting and Tsiolkovsky isn't that high. Spirit can see over it.
I think that any shadows will provide more information to us.

Tried. Rover is oriented North-South (front towards North), and left side lower than the right side (negative roll) about 10-12deg (will know the exact angles in a short while). Therefore we need to take images at sunrise, the ideal time is 6:00-6:10. We got 5 NAVCAMs on the morning of sol 1902 between 5:50 and 6:13 (IIRC) and today (morning of sol 1905) we should have 5 more captured after this set. I have not seen these last 5 images but It looks like the sun is blocked by the top of Home Plate at the time the Sun would be aligned with the belly pan. Sigh.

Hope this helps.

Paolo

Listed under the category "last chance". Hopefully it does not come to this.

Paolo

Wow! You have sharp eyes! Thanks!

Paolo

RoverDriver (Paolo) said: 'Tried'...'Sigh'.

Damn! We were filming a documentary with the BBC today at the Canberra DSN and couldn't get the sun in the right place for the right shot either.

Seems like it will come down to angle of the vehicle and depth of the wheels and some educated estimates of the rocks and surface seen in earlier views.
It would be nice to model this somehow - virtual, graphical or physical.

How much force is the wind exerting on or under the rover deck? Is this a factor in the traction?

Any possibility the RAT or brush could clear a path through the pile of dust?

I really liked the low sun angle shadow idea, but I see how HP blocks the morning sun. But the sun should set in the WSW as we're near the solstice. (Azimuth around 245 degrees if I'm correct.) So sunset would be in this navcam frame:
http://marsrovers.jpl.nasa.gov/gallery/all...C6P1961R0M1.JPG
The bellypan is about 1.25 metres below navcam. The top of Tsiolkovsky, the ridge in that navcam view, is about 20 metres away. That means the ridge would appear only about 3.5 degrees higher from the bellypan than from navcam. So the Sun should appear only about three degrees high when it sets behind the ridge from the point of view of the bellypan.

So even with the 10-12 degree roll angle of the rover in the wrong direction, sunlight can enter the gap under the bellypan at an angle of only 13-15 degrees relative to the plane of the bellypan. In addition, the sunlight would enter the gap not directly west-east, but at an azimuth of about 25 degrees relative to west-east. So the sunlight can enter the left side of the gap and emerge at the front (or enter the back and exit the right side). That means it has less distance to travel under the pan than the full gap width, so is more likely to emerge and give us information with shadows.

So could it be that we might still get some useful images of sunset shadows? Admittedly it depends on what exactly the height and shape of the ground is below the rover. But that's what we want to determine. So mightn't a null result (no sunlight passing through the gap) still give us important info? Ie with a null result we could say something like "the ground under the rover must be at least x cm high"?

I think it's worth a try.


Here're some of the navcams from sol 1902:
http://qt.exploratorium.edu/mars/spirit/na...DNP1982L0M2.JPG
http://qt.exploratorium.edu/mars/spirit/na...DNP1982L0M1.JPG
http://qt.exploratorium.edu/mars/spirit/na...DNP1982L0M1.JPG


I think it's on the "last chance" category too.

Could a shiny and rounded side be put onto MSL's robotic arm to allow looking underneath it? Maybe someone could suggest it to Exomars too?

I believe that traditionally the mirror goes on the toe of the shoe . Not so effective with wheels, though.

Back on sol 373 Oppy's front hazcam caught an interesting reflection from a part of the IDD:
http://marsrovers.jpl.nasa.gov/gallery/all...DIP1144L0M1.JPG
What about maneuvering Spirit's IDD to use it as a mirror to try to image under the belly?

Or, for that matter, what about using the MI to directly image under the belly, if it can be maneuvered in such a way? Of course the focus would be terrible, but we might be able to still get a rough idea of how close we are to high-centreing. Especially if the background beyond the rover is bright, and foreground (ground under the rover) is dark - we could distinguish the foreground in silhouette against the background.

Actually a bit of deconvolution might correct the out-of-focused image. I've had great results with a couple of focus-correcting software apps. But can the IDD face backwards? Using it as a mirror will likely work just fine.